Spatial interaction between retinal and choroidal circulation in retinal vein occlusion.

Retinal vein occlusion (RVO) is a leading cause of vision loss, yet the interaction between retinal and choroidal circulation in this condition remains incompletely understood. This retrospective, cross-sectional study aimed to quantitatively evaluate choroidal structural changes in treatment-naïve unilateral RVO using ultra-widefield imaging. Twenty-nine patients with unilateral branch or central RVO and their unaffected fellow eyes were analyzed. Mean choroidal thickness (MCT) and choroidal vascular index (CVI) were measured on widefield swept-source optical coherence tomography, while choroidal vascular density (CVD) and choroidal vascular fractal dimension (CFD) were calculated from ultra-widefield indocyanine green angiography (UWF-ICGA) images using binarization and fractal analysis protocols. Compared with fellow eyes, RVO eyes demonstrated significantly increased MCT (254.48 ± 60.72 μm vs. 230.68 ± 60.47 μm, P = 0.030), CVI (64.85 ± 3.38 vs. 61.88 ± 4.34, P = 0.011), and CVD (62.24 ± 2.87 vs. 60.01 ± 3.41, P = 0.038), whereas CFD was reduced (1.77 ± 0.02 vs. 1.82 ± 0.02, P < 0.001). Sub-quadrant analysis in branch RVO revealed that choroidal vascular changes were localized to the affected quadrant, with significantly higher CVD and lower CFD than the corresponding quadrants in the same and fellow eyes. These findings suggest that RVO induces regional choroidal vascular remodeling, possibly mediated by VEGF-driven vasodilation and inflammatory pathways, supporting a spatially localized interaction between retinal and choroidal circulation in acute retinal vascular occlusion.